Recently, development of humanoid electric hands that are capable of performing holding operations, similarly to human hands, and serve as electric artificial hands or electric hands for humanoid robots has been advanced. According to humanoid electric hands described in Patent Literatures 1 to 3, for example, respective joints of fingers are driven by wires.
As described above, the wires are employed to drive the conventional humanoid electric hands, so that smooth movement of the fingers is realized while avoiding an increase in weight. However, as the wires stretch when used over a long period of time, it is necessary to replace the wires and string the wires again. Accordingly, there are demands for the humanoid electric hands that are light-weighted and easily maintained.
According to the humanoid electric hand described in Patent Literature 3, a motor having a large output is required to drive the fingers other than the thumb, to secure multiple degrees of freedom and a large holding force. This causes an increase in weight of the electric hand. Further, according to the humanoid electric hands described in Patent Literatures 1 to 3, it is inevitable that operations of wrist portions are performed in an unnatural manner because the wrist portions have no degree of freedom. At the time of holding a cup, for example, it is necessary to lean his or her body to adjust the position of the glass, in order to prevent liquid from spilling out of the cup. Further, according to the humanoid electric hands described in Patent Literatures 1 to 3, control sections are provided outside the electric hands. Therefore, it is necessary to route many cables between the electric hands and the control sections. As a result of this, operations of the electric hands may be limited, and operation reliability of the electric hands may be decreased.